From this comment and the one about the memory wipe I get the feel that there is a notion that hardware-based (anti-tampering) security is the only solution to

From this comment and the one about the memory wipe I get the feel that there is a notion that hardware-based (anti-tampering) security is the only solution to this problem. Isn't a straightforward software solution is to make the PSK write-only or protected by a different, changeable password?